The use of photocurable dental materials in the practice of restorative dentistry has become popular. Photocurable materials are cured by exposure to radiant energy in a preselected spectral range, typically in either the long-wave ultraviolet or blue visible spectrum, tailored to the composition of the photocurable material to be cured. A light-curing unit containing a reflector lamp is used to irradiate the photocurable material by directing light from the reflector lamp through a light guide, with its distal end positioned contiguous to the photocurable material to be cured. The light guide functions to channel the light to the material at the site of a dental restoration, and should lose as little light as possible to the surrounding environment. However, to assure maximum maneuverability of the light guide within the oral cavity, it is desirable for the light guide to be curved at its distal end through an angle which should lie between thirty (30.degree.) and ninety degrees (90.degree.), although an angle of between thirty (30.degree.) and sixty degrees (60') is preferred. To satisfy the curved geometry requirement without suffering a substantial loss in light transmission, particularly through the curved section, it is, at present, conventional to construct the light guide from a fiber-optic conductor. Generally, a fiber-optic conductor consists of either multiple glass fiber strands held together in the form of a "flexible bundle," or fused into a solid rod of individual fibers. The use of multiple glass fiber strands, each small in diameter, permits the fiber-optic rod to be curved with little loss in light transmission. However, the fiber-optic bundle and the fused fiber-optic rod are relatively expensive to manufacture. Moreover, the solid, fused fiber-optic rod, although more desirable, is fragile, and, if dropped, will readily fracture or break.
A solid, optical conductor composed of a transparent, solid, unitary glass or plastic rod having a curved geometry would have significant economic and practical advantages over the conventional fiber-optic rod, provided light could be transmitted through the rod without suffering significant loss in light transmission. Several alternatives to the fiber-optic light guide have been proposed in the prior art such as using a hollow, transmitting, cone-shaped light collector with internal reflecting mirrors, a higher powered light source, or simply ignoring the preference of the dental profession for a contoured light guide with a large angle of curvature at the distal end. These alternatives have not proven to be practical or desirable.